Operation Grange was launched in 2011 after the Portuguese-led investigation was closed in 2008.

It has so far cost more than £11 million.

A Home Office spokesman said: “The Metropolitan Police has made a further application for funding, which will be considered. They have needed to justify what the money would be spent on.

“The Home Office has provided funding for Operation Grange and the resources required are reviewed regularly with careful consideration given before any new funding is allocated.”

WORLD WITNESSES How many Madeleine McCann ‘sightings’ around the world have there been and were any of them taken seriously?

Scotland Yard asked for the extra cash from the Special Grants Committee to “pursue a final line of inquiry” a McCann source revealed, adding: “It gives Kate and Gerry hope that after more than 10 years they may finally find out what happened to their daughter.”

Three-year-old Maddie vanished from a holiday apartment in Portugal’s Praia da Luz in May 2007.

She had been left alone sleeping with her younger twin siblings while her parents were dining in a nearby tapas restaurant.